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34-533: The basin is part of the Rio Grande rift , a north-south sequence of structural basins that have developed where tectonic forces have pulled the Colorado Plateau away from the interior of North America. The basin is partially filled with sediments eroded from the higher ground to the east and west or brought in by the ancestral Rio Grande. The Jemez volcanic field is located on the western margin of

68-429: A downward hinge on the other. Which side of the basin has the major fault or the hinge alternates along the rift. The alternation between these half-grabens occurs along transfer faults, which trend across the rift to connect the major basin-bounding faults and occur between basins or, in places, within basins. The Precambrian basement changes relief sharply in this area, from 8,700 metres (28,500 ft) below sea level at

102-452: A long time, because it provides a north–south route that follows a major river. The Rio Grande follows the course of the rift from southern Colorado to El Paso, where it turns southeast and flows toward the Gulf of Mexico . Important cities, including Albuquerque , Santa Fe , Taos , Española , Las Cruces , El Paso , and Ciudad Juárez , lie within the rift. The Rio Grande rift represents

136-412: A pure-shear rifting mechanism, in which both sides of the rift pull apart evenly and slowly, with the lower crust and upper mantle (the lithosphere ) stretching like taffy . This extension is associated with very low seismic velocities in the upper mantle above approximately 400 kilometres (250 mi) depth associated with relatively hot mantle and low degrees of partial melting. This intrusion of

170-464: Is fairly complex. The fundamental change in the western margin of the North American plate from one of subduction to a transform boundary occurred during Cenozoic time. The Farallon plate continued to be subducted beneath western North America for at least 100 million years during Late Mesozoic and early Cenozoic time. Compressional and transpressional deformation incurred by

204-652: Is home to the San Pedro Parks Wilderness. The district includes the southern portion of the San Pedro Parks Wilderness. Its district office is in Cuba . The Española Ranger District extends from the foothills of Santa Fe, New Mexico to the Pecos Wilderness and borders the towns of Española, New Mexico and Los Alamos, New Mexico . Santa Fe National Forest near Los Alamos is the location of an orienteering map. The Jemez Ranger District

238-538: Is in the south. The crustal thickness underneath the rift is on average 30–35 kilometres (19–22 mi), thinner by 10–15 kilometres (6.2–9.3 mi) than the Colorado Plateau on the west and the Great Plains to the east. Formation of the rift began with significant deformation and faulting with offsets of many kilometers starting about 35 Ma. The largest-scale manifestation of rifting involves

272-691: Is intersected in northern New Mexico by the NE-SW trending Jemez Lineament which extends well into Arizona . The lineament is defined by aligned volcanic fields and several calderas in the area, including the Valles Caldera National Preserve in the Jemez Mountains . The Jemez Lineament is thought to be a hydrous subduction zone scar, separating Precambrian basement rock of the Yavapai - Mazatzal transition zone from

306-506: Is responsible for anomalously high earthquake activity in the vicinity, including the largest rift-associated earthquakes in historic times (two events of approximately magnitude 5.8) in July and November 1906. Earth and space-based geodetic measurements indicate ongoing surface uplift above the Socorro magma body at approximately 2 mm/year. The Rio Grande rift's tectonic evolution

340-455: Is the oldest of the three major basins, and contains 7,350 metres (24,110 ft) of Paleogene clastic sediments deposited on Precambrian basement. The southernmost Albuquerque basin contains pre-rift volcanic deposits , while the central and northern portions contain volcanics erupted during rifting. In cross-section, the geometry of the basins within the rift are asymmetrical half-grabens , with major fault boundaries on one side and

374-628: The Laramide Orogeny lasted until about 40  Ma in New Mexico. This deformation may have been a result of the coupling between the subducting Farallon plate and the overlying North American Plate . Crustal thickening occurred due to Laramide compression. After the Laramide Orogeny and until 20 Ma, a major period of volcanic activity occurred throughout the southwestern United States. Injection of hot magmas weakened

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408-610: The Valles Caldera National Preserve , which is administered by the National Park Service. Bandelier National Monument was created from a portion of Santa Fe in 1916, but additional land was added to Bandelier from land that was formerly part of Los Alamos National Laboratory and from land that was owned by the Dunnigans when they owned the Baca Ranch. The Coyote Ranger District is the northernmost district of

442-673: The asthenosphere into the lithosphere and continental crust is thought to be responsible for nearly all of the volcanism associated with the Rio Grande rift. The sedimentary fill of the basins consists largely of alluvial fan and mafic volcanic flows. The most alkalic lavas erupted outside the rift. The sediments that were deposited during rifting are commonly known as the Santa Fe Group . This group contains sandstones , conglomerates , and volcanics. Aeolian deposits are also present in some basins. The Rio Grande rift

476-407: The lithosphere was hot, the brittle-ductile transition was relatively shallow. There is evidence that the second period of extension began earlier in the central and northern Rio Grande rift than in the south. A third period of extension may have begun in the early Pliocene . One theory is that the Colorado Plateau acts as a semi-independent microplate and one way of explaining the creation of

510-664: The Mazaztl Province proper. Also on the Colorado Plateau but further north lies the San Juan volcanic field in the San Juan Mountains of Colorado. The youngest eruptions in the rift region are in the Valley of Fires , New Mexico, and are approximately 5,400 years old. The Socorro, New Mexico , region of the central rift hosts an inflating mid-crustal sill-like magma body at a depth of 19 km that

544-426: The Rio Grande rift is by the simple rotation of the Colorado Plateau 1-1.5° in a clockwise direction relative to the North American craton. Other explanations that have been offered are that the extension is driven by mantle forces, such as large-scale mantle upwelling or small-scale mantle convection at the edge of the stable craton; collapse of over-thickened continental crust; initiation of transform faulting along

578-672: The San Luis is roughly 120 by 80 kilometres (75 by 50 mi). These basins may contain smaller units within them, such as the Alamosa basin within the San Luis, which is bounded by the San Juan and Tusas mountains on the west and the Sangre de Cristo Mountains in the east. The Albuquerque basin is the largest of the three basins, spanning 160 kilometres (99 mi) north–south and 86 kilometres (53 mi) east–west at its widest points. It

612-726: The Santa Fe National Forest and covers 265,100 acres (1073 km ). It includes the Rio Chama and most of the Chama River Canyon Wilderness (with a small part extending into neighboring Carson National Forest ), as well as the northern portion of the San Pedro Parks Wilderness . The district office is in the town of Coyote . The Cuba Ranger District is in the westernmost district of the Santa Fe National Forest and

646-471: The basin and has contributed additional volcanic sediments to the basin. The sediments formed the Tesuque Formation and Chamita Formation of the Santa Fe Group . The basin began forming during the middle to late Oligocene , around 25 million years ago. The early basin was more extensive than the present basin, and there is no evidence of boundary faults at this stage of development. The basin

680-627: The basin center, there is are thick beds of older sedimentary rock that may be an old lake deposit of the Eocene Galisteo or El Rito Formations . The deepest portion of the rift is along the Velarde graben, which is up to 5 km deep. The Rio Grande became established in the basin in the Pliocene , around 4 million years ago. Volcanic activity in the Cerros del Rio periodically dammed

714-408: The basin. This aquifer is under stress from urban development and drought and the basin has been heavily studied to permit better management of this resource. Geophysical measurements show a deep layer of sedimentary rock in the basin, and this has been the target of exploratory drilling for petroleum . However, the beds were found to most likely be relatively young (Eocene) lake sediments rather than

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748-500: The bottom of the Albuquerque basin to 3,300 metres (10,800 ft) above sea level in the nearby Sandia Mountains , which flanks the Albuquerque basin to the east. Flanking mountains are generally taller along the east side of the rift (although some of this relief may be Laramide in origin). The thickness of the crust increases to the north beneath the rift, where it may be as much as 5 kilometres (3.1 mi) thicker than it

782-548: The city of Santa Fe . Santa Fe National Forest was established on July 1, 1915 by the U.S. Forest Service with the amalgamation of Jemez National Forest to the west of Santa Fe and Pecos National Forest to the east. The former division is remembered in the ranger districts, with the Jemez Ranger District to the west and the Pecos/Las Vegas district to the east. The western district is adjacent to

816-555: The city of Los Alamos, at the feet of the Jemez Mountains . The basin is an asymmetric half-graben , with the beds within the basin dipping to the west. No major bounding faults are found on the east side of the basin. The accumulated sediments in the center of the basin are about 2 to 3 km thick, becoming thinner to the east and pinching out against the Precambrian rock of the Sangre de Cristo Mountains. At greater depths near

850-532: The easternmost manifestation of widespread extension in the western U.S. during the past 35 million years. The rift consists of three major basins and many smaller basins, less than 100 square kilometres (39 sq mi). The three major basins (from northernmost to southernmost) are the San Luis , Española , and Albuquerque basins. The rift's northern extent is delineated by the upper Arkansas River basin between Leadville and Salida, Colorado . Further south,

884-439: The lithosphere and allowed for later extension of the region. Cenozoic extension started about 30 million years ago (Ma). There are two phases of extension observed: late Oligocene and middle Miocene . The first period of extension produced broad, shallow basins bounded by low-angle faults. The crust may have been extended as much as 50% during this episode. Widespread magmatism in mid- Cenozoic time suggests that

918-404: The north to the state of Chihuahua , Mexico , in the south. The rift zone consists of four basins that have an average width of 50 kilometres (31 mi). The rift can be observed on location at Rio Grande National Forest , White Sands National Park , Santa Fe National Forest , and Cibola National Forest , among other locations. The Rio Grande rift has been an important site for humans for

952-421: The petroleum-bearing Mesozoic or Paleozoic beds that were hoped for. 35°54′N 106°06′W  /  35.9°N 106.1°W  / 35.9; -106.1 Rio Grande rift The Rio Grande rift is a north-trending continental rift zone. It separates the Colorado Plateau in the west from the interior of the North American craton on the east. The rift extends from central Colorado in

986-527: The rift is defined by a network of smaller, less topographically distinct alternating basins and ranges. The distinction between these smaller basins and those of the Basin and Range Province becomes blurred in northern Mexico . Basin size generally decreases to the north in the rift, though the Española covers approximately 120 kilometres (75 mi) north–south and 40 kilometres (25 mi) east–west, and

1020-479: The river and created a large lake in the Espanola basin. The Espanola basin has yielded vertebrate fossils since the 1870s, which provide the most extensive Miocene fossil record in New Mexico. Most of the fossils are mammals, but lizard and turtle fossils have also been recovered, along with freshwater diatoms . The sediments beneath the basin form a major regional aquifer supplying water to most residents of

1054-532: The summit of Truchas Peak , located within the Pecos Wilderness . The Jemez, Coyote, and Cuba districts are located in the Jemez Mountains ; the Pecos/Las Vegas district is located in the Sangre de Cristo Mountains ; and the Española district is located in both mountain ranges. In descending order of land area the forest lies in parts of Rio Arriba , San Miguel , Sandoval , Santa Fe , Mora , and Los Alamos counties. Forest headquarters are located in

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1088-642: The western margin of the North American plate; or detachment of a fragment of the Farallon plate beneath the Rio Grande region that enhanced asthenospheric upwelling in the slab window. Santa Fe National Forest The Santa Fe National Forest is a protected national forest in northern New Mexico in the Southwestern United States . It was established in 1915 and covers 1,558,452 acres (6,306.83 km ). Elevations range from 5,300 feet (1600 m) to 13,103 feet (4000 m) at

1122-842: Was established in 1905 as the Jemez Forest Reserve . A number of hot springs and the Jemez Soda Dam on the Jemez River are among the attractions, along with the Dome Wilderness , which lies just west of Bandelier National Monument . The district office is in Jemez Springs . The Pecos/Las Vegas Ranger District was established in 1892 as the Pecos River Forest Reserve . The easternmost element of Santa Fe National Forest includes

1156-524: Was likely a shallow depression between the Sierra Nacimiento to the west and the Sangre de Cristo Mountains to the east. Faulting and volcanism began on the west side of the basin in mid-Miocene time, around 14 million years ago. In the early Pliocene , rifting became focused on the Velarde graben, which is bounded on the west by the Pajarito fault zone. This is located on the western edge of

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